/*-------------------------------------------------------------------------
 *
 * dllist.h--
 *      simple doubly linked list primitives
 *      the elements of the list are void* so the lists can contain
 *      anything
 *      Dlelem can only be in one list at a time
 *     
 *
 *   Here's a small example of how to use Dllist's :
 * 
 *   Dllist *lst;
 *   Dlelem *elt;
 *   void   *in_stuff;    -- stuff to stick in the list
 *   void   *out_stuff
 *
 *   lst = DLNewList();                -- make a new dllist
 *   DLAddHead(lst, DLNewElem(in_stuff)); -- add a new element to the list
 *                                           with in_stuff as the value
 *    ...  
 *   elt = DLGetHead(lst);             -- retrieve the head element
 *   out_stuff = (void*)DLE_VAL(elt);  -- get the stuff out
 *   DLRemove(elt);                    -- removes the element from its list
 *   DLFreeElem(elt);                  -- free the element since we don't
 *                                        use it anymore
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 * $Id: dllist.h,v 1.3 1996/11/10 03:05:16 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */

#ifndef DLLIST_H
#define DLLIST_H


struct Dllist;
struct Dlelem;

typedef struct Dlelem {
  struct Dlelem *dle_next;  /* next element */
  struct Dlelem *dle_prev;  /* previous element */
  void   *dle_val; /* value of the element */
  struct Dllist *dle_list;  /* what list this element is in */
} Dlelem;

typedef struct Dllist {
  Dlelem *dll_head;
  Dlelem *dll_tail;
} Dllist;
  
extern Dllist* DLNewList(void); /* initialize a new list */
extern void    DLFreeList(Dllist*); /* free up a list and all the nodes in it*/
extern Dlelem* DLNewElem(void* val); 
extern void    DLFreeElem(Dlelem*); 
extern Dlelem* DLGetHead(Dllist*);
extern Dlelem* DLGetTail(Dllist*);
extern void*   DLGetHeadVal(Dllist*);
extern void*   DLGetTailVal(Dllist*);
extern Dlelem* DLGetPred(Dlelem*); /* get predecessor */
extern Dlelem* DLGetSucc(Dlelem*); /* get successor */
extern void    DLRemove(Dlelem*); /* removes node from list*/
extern void    DLAddHead(Dllist* list, Dlelem* node);
extern void    DLAddTail(Dllist* list, Dlelem* node);
extern Dlelem* DLRemHead(Dllist* list); /* remove and return the head */
extern Dlelem* DLRemTail(Dllist* list); /* remove and return the tail */

#define DLE_VAL(x)  (x->dle_val)

#endif /* DLLIST_H */
